The addition of small molecules to (η-C5H5)2Rh2(CO)(CF 3C2CF3). X. Addition of terminal alkynes; the formation of bridging carbonyl cyclobutenyl intermediates (η-C5H5)2Rh2(μ-CO)-[ η13-C4(CF3)HR] and their facile conversion to binuclear metalladine complexes (η-C5H5)2Rh24-C4(CF3)2HR].

Ron S. Dickson, Felicity I. McLure, Rhonda J. Nesbit

Research output: Contribution to journalArticlepeer-review

Abstract

Reaction occurs immediately when solutions of (η-C5H5)2Rh2(μ-CO)( μ-η2-CF3C2CF3) (1) in hexane are treated with HCCR (R = H, CF3 or Ph), and the cyclobutenyl complexes (η-C5H5)2Rh2(μ-CO) [μ-η13-C4(CF3) 2HR] (2) separate in near quantitative yield. CO is lost fairly rapidly from solutions of 2 in polar organic solvents, and the metallacyclopentadiene complexes (η-C5H5)2Rh2[μ-η 24-C4(CF3)2 H R] (3) are formed. The reactions between HCCR (R = Pr or CH2CO2Me) and 1 in hexane are also fast, but no precipitate is formed; infrared spectroscopy indicates that 2 (R = Pr or CH2CO2Me) is present in the reaction solution, but there is rapid conversion into 3 (ca. 80% yield after TLC work up). Slower reactions (2-5 min) occur between 1 and HCCR (R = CH2CH2CH2CCH or CMe=CH2) in hexane, and again all the products remain in solution. It is possible to separate 2 (R = CH2CH2CH2CCH or CMeCH2) (up to 65% yield obtained) from the corresponding 3 by immediate TLC, but 2 is converted fairly rapidly into 3 when left in solution. The reaction between 1 and HCCSiMe3 is significantly slower (ca. 15 min), and gives 3 (R = SiMe3) (64% yield) and (η-C5H5)2Rh2(CO)2 CF3C2CF3 (21%) as major products. Another product, spectroscopically identified as (η-C5H5)2Rh2(μ-CO) [μ-C(O)C(CF3)C(CF3)](μ-HC2SiMe 3 ) (7) can be isolated in significant amount only when TLC of the reaction solution is performed within 10 min of mixing the reactants. Spectroscopic analysis indicates complete regioselectivity in the formation of all metallacyclopentadiene complexes 3, with the H and R groups (from HCCR) located in the 3- and 2-positions respectively of the 1-metallacyclopentadiene ring.

Original languageEnglish
Pages (from-to)413-426
Number of pages14
JournalJournal of Organometallic Chemistry
Volume349
Issue number3
DOIs
Publication statusPublished - 26 Jul 1988
Externally publishedYes

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